The electrical conductivity of a metal has the SI units Siemens/meter. This is a reciprocal of the resistivity that is expressed in terms of ohm*m.
Electrical conductivity of a metal is not the same at all temperatures. It varies both when there is a change in temperature as well as when there is a change in composition. For example when two metals are mixed or an impurity is added to create an alloy.
The most conductive pure metal is silver. This is what makes it the metal that is used in the construction of integrated circuits and in electronics whenever a path with a very low resistance is needed. On the other hand pure mercury has the lowest conductivity.
You can see the conductivity of different metals in the list provided below.